Winter annual weeds are now starting to rear their ugly heads. Fall is an excellent time to get a jump start on them prior to next spring with several options.
For residual control, consider atrazine. If going to corn, other residual herbicide options include an ALS herbicide such as Autumn or Basis. ALS-resistant marestail will survive Autumn or Basis treatment if applied alone. For burndown, producers should mix in 2,4-D and/or glyphosate. Aim and Rage D-Tech are other non-residual, contact herbicide options.
One half to two pounds (maximum) per acre of atrazine, usually with 1 to 2 pint/acre of 2,4-D LV4 or LV6 added, can give good burndown of winter annual broadleaf weeds--such as henbit, Virginia pepperweed, prickly lettuce, field pansy, evening primrose, and marestail--and small non-tillered winter annual grasses. Atrazine residual should control germinating winter annual broadleaves and grasses. When higher rates of atrazine are used, there should be enough residual effect of the fall-applied atrazine to control early-spring germinating summer annual broadleaf weeds such as kochia, lambsquarters, wild buckwheat, and Pennsylvania smartweed.
Tank mixing 2,4-D with atrazine enhances control of all broadleaf species. It is especially important for common dandelion, henbit, marestail, and prickly lettuce control. The low-volatile ester formulations should be used, as they tend to be more potent than amine formulations, pound for pound. While it is always important to manage herbicide drift, herbicide applications made after fall frost have less potential for drift problems.
If fall treatments control volunteer wheat, winter annuals, and early-emerging summer annuals right up to planting corn or sorghum, then at planting time only a light preplant tillage or a pre-emerge grass and broadleaf herbicide application with glyphosate or paraquat will be needed to catch newly emerged weeds. Soils will be warmer and easier to plant where winter weeds were controlled in fall. Fall applications during the last couple of weeks of October and through November can greatly assist control of difficult winter annuals and should be considered when performance of spring preplant weed control has not been adequate.
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